[PATCH 13/27] ext4: add a new iomap aops for regular file's buffered IO path

Zhang Yi
2024-10-22T03:13:02Z

From: Zhang Yi <yi.zhang@huawei.com>

This patch starts support for iomap in the buffered I/O path of ext4
regular files. First, it introduces a new iomap address space operation,
ext4_iomap_aops. Additionally, it adds an inode state flag,
EXT4_STATE_BUFFERED_IOMAP, which indicates that the inode uses the iomap
path instead of the original buffer_head path for buffered I/O. Most
callbacks of ext4_iomap_aops can directly utilize generic
implementations, the remaining functions .read_folio(), .readahead(),
and .writepages() will be implemented in later patches.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
fs/ext4/ext4.h | 1 +
fs/ext4/inode.c | 32 ++++++++++++++++++++++++++++++++
2 files changed, 33 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 44f6867d3037..ee170196bfff 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1916,6 +1916,7 @@ enum {
EXT4_STATE_VERITY_IN_PROGRESS, /* building fs-verity Merkle tree */
EXT4_STATE_FC_COMMITTING, /* Fast commit ongoing */
EXT4_STATE_ORPHAN_FILE, /* Inode orphaned in orphan file */
+ EXT4_STATE_BUFFERED_IOMAP, /* Inode use iomap for buffered IO */
};

#define EXT4_INODE_BIT_FNS(name, field, offset) \
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1ccf84a64b7b..b233f36efefa 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3526,6 +3526,22 @@ const struct iomap_ops ext4_iomap_report_ops = {
.iomap_begin = ext4_iomap_begin_report,
};

+static int ext4_iomap_read_folio(struct file *file, struct folio *folio)
+{
+ return 0;
+}
+
+static void ext4_iomap_readahead(struct readahead_control *rac)
+{
+
+}
+
+static int ext4_iomap_writepages(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ return 0;
+}
+
/*
* For data=journal mode, folio should be marked dirty only when it was
* writeably mapped. When that happens, it was already attached to the
@@ -3612,6 +3628,20 @@ static const struct address_space_operations ext4_da_aops = {
.swap_activate = ext4_iomap_swap_activate,
};

+static const struct address_space_operations ext4_iomap_aops = {
+ .read_folio = ext4_iomap_read_folio,
+ .readahead = ext4_iomap_readahead,
+ .writepages = ext4_iomap_writepages,
+ .dirty_folio = iomap_dirty_folio,
+ .bmap = ext4_bmap,
+ .invalidate_folio = iomap_invalidate_folio,
+ .release_folio = iomap_release_folio,
+ .migrate_folio = filemap_migrate_folio,
+ .is_partially_uptodate = iomap_is_partially_uptodate,
+ .error_remove_folio = generic_error_remove_folio,
+ .swap_activate = ext4_iomap_swap_activate,
+};
+
static const struct address_space_operations ext4_dax_aops = {
.writepages = ext4_dax_writepages,
.dirty_folio = noop_dirty_folio,
@@ -3633,6 +3663,8 @@ void ext4_set_aops(struct inode *inode)
}
if (IS_DAX(inode))
inode->i_mapping->a_ops = &ext4_dax_aops;
+ else if (ext4_test_inode_state(inode, EXT4_STATE_BUFFERED_IOMAP))
+ inode->i_mapping->a_ops = &ext4_iomap_aops;
else if (test_opt(inode->i_sb, DELALLOC))
inode->i_mapping->a_ops = &ext4_da_aops;
else
--
2.46.1